Conventionally, radar antennas each including an antenna unit and a housing unit has been known. The antenna unit radiates outside radio waves. The housing unit is built therein with a motor for rotating the antenna unit, a coaxial cable for supplying radio waves to the antenna unit, etc.
Moreover, various kinds of antenna units have conventionally been known, such as, an antenna unit having a shape in which the cross-section of an opening part thereof becomes gradually spreads wider toward outside (horn shape, trumpet shape). In supporting the horn-shaped antenna unit, it has been known that even if a metal is disposed right beneath or behind the horn part, it does not give any influence on a beam formation. Therefore, conventionally, in order to stably support the horn-shaped antenna unit, the antenna unit is generally substantially directly attached to the housing unit (with an attaching plate interposing therebetween).
Moreover, JP1991-042723A discloses an antenna unit having dielectric bodies. The antenna unit includes a dielectric body waveguide mechanism comprised of two dielectric body flat plates opposing to each other.
However, with the antenna unit having the dielectric bodies as disclosed in JP1991-042723A, when a metal is disposed near the antenna unit, a beam cannot be formed appropriately. Therefore, the antenna unit having the dielectric bodies is preferred not to be disposed near the housing body, which is different from the conventional horn-shaped antenna unit.
Therefore, the antenna unit having the dielectric bodies is preferred to be supported to be separated from the housing unit. However, in this case, it is concerned that a coaxial cable or the like connecting the antenna unit with the housing unit will be exposed outside.
Thus, an ultraviolet ray countermeasure is needed for the part of the coaxial cable exposed outside. Moreover, when applying to a ship radar apparatus, since it is concerned that the exposed cable receives seawater and a stress due to air pressure, a countermeasure for these factors is also needed. As a result, the manufacturing cost of the radar antennas increases.
Moreover, in the case where the coaxial cable is exposed outside, the appearance of the radar antenna will seem untidy and it is not preferable also in view of the design.
However, JP1991-042723A only discloses the configuration having the shape of the antenna unit with the dielectric bodies, and the details in connecting or protecting the coaxial cable and a waveguide are not disclosed.